Free PS4 games
PlayStation Plus:

    Call of Duty: Modern Warfare 2 Campaign Remastered
    Fall Guys

Free Xbox One games

    Crackdown
    Crackdown 2
    Too Human

Xbox Live Gold:

    Dunk Lords
    Portal Knights
    MX Unleashed

Free Nintendo Switch games

    Jump Rope Challenge

Free PC games
Epic Games Store:

    The Alto Collection
    Remnant: Rise From Ashes
    A Total War Saga: Troy

Twitch Prime:

    Art of Fighting 2
    Baseball Stars 2
    Blazing Chrome
    Blazing Star
    Chroma Squad
    Dead in Vinland
    Dungeon Rushers
    Fatal Fury Special
    Ironclad
    The King of Fighters 2000
    The King of Fighters 2002
    King of the Monsters
    Metal Slug 2
    NeuroVoider
    Pulstar
    Samurai Shodown 2
    Sengoku 3
    Shaq Fu: A Legend Reborn
    Shock Troopers 2nd Squad
    SNK 40th Anniversary Collection
    Treachery in Beatdown City
    Truberbrook
    Warsaw

GOG:

    Akalabeth: World of Doom
    Alder's Blood Prologue
    Ascendant
    Beneath a Steel Sky
    Bio Menace
    Builders of Egypt: Prologue
    Cayne
    Delores: A Thimbleweed Park Mini-Adventure
    Doomdark's Revenge
    Eschalon: Book I
    Flight of the Amazon Queen
    Hello Neighbor Alpha Version
    Jill of the Jungle: The Complete Trilogy
    Legend of Keepers: Prologue
    The Lords of Midnight
    Lure of the Temptress
    Postal: Classic and Uncut
    Sang-Froid: Tales of Werewolves
    Shadow Warrior Classic Complete
    Stargunner
    Sunrider: Mask of Arcadius
    Teenagent
    Treasure Adventure Game
    Tyrian 2000
    Ultima 4: Quest of the Avatar
    Ultima Worlds of Adventure 2: Martian Dreams
    War Wind
    Worlds of Ultima: The Savage Empire

Uplay:

    Might & Magic Chess Royale
    Rabbids Coding

Itch.io:

    Becalm
    Death Ray Manta SE
    Fjords
    From Orbit
    The Restless
    The Things We Lost In The Flood

Free Stadia Games
Stadia Pro

    Crayta: Premium Edition
    Destiny 2
    Get Packed
    Grid
    Gylt
    Just Shapes & Beats
    Kona
    Little Nightmares
    Metro 2033 Redux
    Monster Boy and the Cursed Kingdom
    Orcs Must Die! 3
    Panzer Dragoon: Remake
    Power Rangers: Battle for the Grid
    PUBG
    Spitlings
    SteamWorld Dig
    SteamWorld Dig 2
    SteamWorld Heist
    SteamWorld Quest
    Strange Brigade
    Superhot
    The Turing Test
    West of Loathing
    Zombie Army 4: Dead War